1. Field of the Invention
The present invention relates generally to methods for fabricating magnetic heads for hard disk drives, and more particularly to devices and methods for preventing electrostatic discharge (ESD) damage to magnetoresistive read head elements during the manufacturing of such magnetic heads.
2. Description of the Prior Art
Thin film heads are particularly susceptible to damage from electrostatic discharge. A major problem that is encountered during manufacture, handling and use of magnetic recording heads is the buildup of electrostatic charges on the various elements of a head or other objects which come into contact with the heads and the accompanying spurious discharge of the static electricity thus generated. For example, static charges may be produced at various steps during wafer processing. The build up of the static charge can cause the breakdown of the read gaps, leading to the shorting of the read sensor to its adjacent shields or the damage of the sensor itself.
Magnetoresistive (MR) sensors are well known and are particularly useful as read elements in magnetic heads, especially at high recording densities. The MR read sensor provides a higher output signal than other types of read heads. This higher output signal results in a higher signal to noise ratio for the recording channel, and thus allows greater areal density of recorded data on a magnetic disk surface to be achieved. As described above, when an MR sensor is exposed to ESD, or even a voltage or current input larger than that intended under normal operating conditions, referred to as electrical overstress or EOS, the MR read sensor and other parts of the head may be damaged. This sensitivity to electrical damage is particularly severe for MR read sensors because of these sensors"" relatively small physical size. For example, an MR sensor used for extremely high recording densities will have an area of approximately 0.5 by 0.3 microns or smaller. The nature of the damage which may be experienced by an MR sensor varies significantly, including complete destruction of the sensor via melting and evaporation, contamination of the air bearing surface, generation of shorts via electrical breakdown, and milder forms of damage in which the head performance may be degraded. These types of damages have been found to occur during both processing and use and poses a serious problem in the manufacturing and handling of magnetic heads incorporating MR read sensors.
To protect the MR read head element from ESD damage during wafer level manufacturing, a lead from the MR element is electrically connected to one or both of the read head element shields during manufacturing. In a preferred embodiment of the present invention, the electrical connection is fabricated in the kerf area between adjacent magnetic heads as they are fabricated upon a wafer substrate. Thereafter, when the magnetic heads are separated by saw cutting through the kerf areas, the electrical connections are thereby removed, such that the MR element electrical leads and the shields are electrically isolated. In an alternative embodiment, one or more of the shields, as well as the MR element leads can also be electrically connected to the substrate upon which the magnetic head is fabricated. In further alternative embodiments, the electrical connection between one or more of the shields and the MR element electrical lead can be fabricated within the magnetic head area, rather than in the kerf area, and a suitable resistance is fabricated into the interconnecting circuit. In this embodiment, the electrical interconnection between the MR element electrical lead and one or more of the shields has a pre-designed electrical resistance and it remains in the magnetic head following fabrication.
It is an advantage of the present invention that electrostatic damage to the MR element is minimized during manufacturing.
It is another advantage of the present invention that the electrical connection between the MR element electrical leads and one or more of the shields is fabricated by altering one or more of the masks that are utilized in fabricating the magnetic head.
It is a further advantage of the present invention that the electrical connection between the MR element electrical lead and one or more of the shields is severed following manufacturing by the magnetic head separation process, such that no additional manufacturing step is required to sever the electrical connection.